add time based policy

Author: resmo

docs/policy_configs.md

@@ -44,6 +44,32 @@ policy:
   target: 5
 ```
 
+## Time Policy
+
+Time based scaling, scaling during time ranges.
+
+```yaml
+policy:
+- name: Scaling up at 7 a.m. by factor 2 (pre-heating for known load)
+  source: time
+  target: 2
+  config:
+    start_time: "06:58"
+    end_time: "07:00"
+    metric: 1
+```
+
+```yaml
+policy:
+- name: Scaling down during night
+  source: time
+  target: 1
+  config:
+    start_time: "22:00"
+    end_time: "05:00"
+    metric: 10
+```
+
 ## Random Policy
 
 For testing purpose, random metric to get some action.

sample/config.yaml

@@ -29,6 +29,22 @@ policies:
       start: 1
       stop: 10
 
+  - name: Scaling up at 7 a.m. by factor 3
+    source: time
+    target: 3
+    config:
+      start_time: "06:58"
+      end_time: "07:00"
+      metric: 1
+
+  - name: Scaling down during night by factor 0.1
+    source: time
+    target: 1
+    config:
+      start_time: "22:00"
+      end_time: "06:59"
+      metric: 10
+
 cloud:
   ### Cloudscale.ch
   kind: cloudscale_ch

scalr/policy/adapters/time.py

@@ -0,0 +1,33 @@
+from datetime import datetime
+
+from scalr.log import log
+from scalr.policy import PolicyAdapter
+
+
+def in_between(current, start, end):
+    if start <= end:
+        return start <= current < end
+    else:  # over midnight e.g., 23:30-04:15
+        return start <= current or current < end
+
+
+class TimePolicyAdapter(PolicyAdapter):
+    def get_current(self) -> float:
+        target = self.config.get("target", 1)
+
+        now = datetime.now().time().strftime("%H:%M")
+        log.info(f"Now, it is {now}")
+        current = datetime.strptime(now, "%H:%M")
+
+        start_time = self.config.get("start_time", "")
+        end_time = self.config.get("end_time", "")
+
+        start = datetime.strptime(start_time, "%H:%M")
+        end = datetime.strptime(end_time, "%H:%M")
+
+        if in_between(current, start, end):
+            log.info(f"Time is between {start_time} and {end_time}")
+            return self.config.get("metric", target)
+
+        log.info(f"Time is not between {start_time} and {end_time}")
+        return 0

scalr/policy/factory.py

@@ -2,6 +2,7 @@
 from scalr.policy import PolicyAdapter
 from scalr.policy.adapters.dummy import DummyPolicyAdapter
 from scalr.policy.adapters.prometheus import PrometheusPolicyAdapter
+from scalr.policy.adapters.time import TimePolicyAdapter
 from scalr.policy.adapters.web import WebPolicyAdapter
 
 
@@ -11,6 +12,7 @@ class PolicyAdapterFactory:
         "dummy": DummyPolicyAdapter,
         "prometheus": PrometheusPolicyAdapter,
         "web": WebPolicyAdapter,
+        "time": TimePolicyAdapter,
     }
 
     @staticmethod

scalr/scalr.py

@@ -67,7 +67,7 @@ def get_factor(self, policy_configs: List[PolicyConfig]) -> float:
             policy_factor: float = policy.get_scaling_factor()
             log.debug(f"Policy scaling factor: {policy_factor}")
 
-            if policy_factor == 0:
+            if policy_factor <= 0:
                 log.debug(f"Ignoring factor 0, keep current scaling factor: {scaling_factor}")
                 continue